The virtual explosion of sophisticated services that can be offered to present subscribers of telecommunications services is due in large part to the network architecture developed by AT&T in which a separate and dedicated Common Channel Signaling System 7 (SS7) network is used to transport out of band trunk signaling and database messages separate from customer voice or data messages transported over the telecommunications network.
Signaling System 7 (SS7) has been widely characterized as a new functional protocol element for a telecommunications network that is the key to ubiquitous deployment of advanced services. V. K. Batra, in an article entitled "The Building Block for the Intelligent Network", Telephony, Vol. 217, No. 22, p. 56 et. seq., Nov. 20, 1989, states that the SS7 network, which is based on the North American version of the CCITT Signaling System 7 protocol, will be the standard protocol for reliable, bidirectional communications between intelligent network nodes using packet switching techniques. An article by T. Lanning entitled "SS7 Interconnection Awaits Green Light", Telephony Suppl. p. 32, 34, November 1990, states that common channel signaling interconnection according to the SS7 protocol will increase network efficiency, reduce basic call setup time and make possible the creation of new services on a nationwide basis. Ultimately, it will pave the way for the evolution of the Advanced Intelligent Network and establish a framework for further advances in the integrated services digital network (ISDN). An instructive survey article containing many supporting references is entitled "Common Channel Signaling-Key to Control of Modern Telecommunications Networks" by R. L. Simms, GLOBECOM '86, IEEE Global Telecommunications Conference Record, p. 623-6 Vol. 1, 1986.
Because it has been recognized that SS7 network architectures concentrate valuable and proprietary information in centralized network databases, it has been found desirable to arrange gateways to screen SS7 messages to ensure network security. This is described, for example, in an article entitled "SS7 Gateways Serve and Protect" by C. Buckles, which appeared in Telephony, Vol. 217, No. 22, p. 39-41, 44, dated Nov. 20, 1989. According to the author, the gateway, which is implemented in the signal transfer point, also supports internetwork routing and exchange of network management messages that communicate the status of interconnected SS7 networks. Further, the gateway collects and reports measurement data on the gateway screening activity.
The importance of SS7 networks to telecommunications has led certain independent telephone companies (ICOs) to choose to implement their own compatible signaling systems so that they can easily communicate with both interexchange carriers such as AT&T as well as Regional Bell Operating Companies (RBOCs). This is described in an article entitled "Common Channel Signaling for Independents" by Hilton and Buckles, which appeared in Telephone Engineer and Management, Vol. 92, No. 12, p. 71-4, dated Jun. 15, 1988.
However, many ICOs, and other entities that own or provide private networks, cannot at present avail themselves of the features and full advantages of the SS7, due in part to budgetary reasons. This is because establishing and maintaining a broad-based signaling network is extremely expensive. Therefore, these network entities may have very limited SS7 capabilities.